Deborail

My Dapol Class 121 recently won’t run. It will make a whining sound and run very slowly or stop. The motor is obviously running but somehow the energy is not being transferred to the wheels.

When the irregular behaviour starts the current spikes to 1.0 - 1.5A and the DSO across the rails displays this. Then the decoder does it’s protection thing and the current drops back to the normal 100 mA or so. Seeing these seesaws on the waveform can one assume an internal problem in the motor?

It’s not easy to send it back to the uk.

Further experiments showed that in dc and in DCC using either a imperious or a ESU decoder the loco has a problem. It draws a lot of current starting at 300 mA then in a few seconds going up to and settling to 1A which is really excessive. Then it stops. The lights flicker faintly. The current drops to zero. The decoder probably shuts itself down. Next power up the cycle repeats. Examination of the PCB has not shown anything abnormal.

I have I stalled a new ESU decoder in my new Royal Mail class 128 DPU and it works fine-confirming that the earlier locomotive had a fault. Installed it with the CV29 value as ‘2’ address ‘28’...for some reason it wouldn’t move if I set the address to ‘128’. I think that is because in AD2 that would be considered as ‘0’

I am not sure mate, but anyway, I am posting it back to the Seller today, it is the Scooby Doo Weathered version. I have found a Royal Mail version on ebay and purchased it. I also ordered a few ESU decoders. Hope for the best going forward...

He said that he prefers to refund.

I have decided to return the locomotive to the seller for a refund. I think I lost three decoders, but I have a feeling that I would lose more going forward using this locomotive. I will source out another 128 later on...hopefully that would work well with DCC.

I will try Lenz. If it blows this too I will let it be a DC loco.

I have contacted Heljan and they said that their motors need robust decoders such as ESU. I was told to use ESU. They said cheaper decoders cannot handle the load of the motor on this locomotive. So far the decoders used were digitrax and a couple of Dapol Imperiums

Thanks for the very eye opening information. I have lifted the PCB which is mildly stuck onto a black plastic surface. I have added a layer of insulation tape just in case. The underside of the pins does not show any soldering overlaps. Pins 1 and 22 do not seem to be shorted. The motor pins 19 and 18 have a suitable resistance between them. All seems very normal. The problem is that to test any further would run me the risk of blowing more decoders. I am getting resigned to the fact that this is destined to become a DC only loco.

It is also surprising to me that this would happen on the programming track, but it did during the programming of the third blown decoder. And the locomotive did move forward as well. It moved significantly. However I have tested other locomotives and decoders on the programming track and all is normal so I don’t believe there is something wrong in the programming track.

Yes, with the blanking plug removed there is no continuity from the track or wheels to the motor connections whether bogies are straight or pivoted ...

Make it three decoders. It has fried a third one on the programming track. I decided to try one more. Still operates fine with the blanking chip in DC mode though. Current draw in DC mode is 300 mA tops. the metal chassis is not electrically connected to the rails. DSO does not show any abnormal wave pattern. I will try to ask Heljan for help before burning any more decoders.

You’re right . but I get a message of ‘writing is completed OK’ on the controller. All the loco lights flash during the writing job.